Thanks for catching this - Intel appear to have re-used cpu branding
strings between Northwood and Prescott pentium4s. Which is just...
special and annoying.
cpuflags now handles this by explicitly testing for SSE3 support to
distinguish between '-march=prescott' and '-march=pentium4' fixed in
v1.32 and apologies for the pain...

I have the fallback for 'core2' as 'pentium-m' which I think
may be better for instruction scheduling, but omits the
SSE3 support of 'nocona'. On balance I think 'nocona' is
probably a better choice.
Could you test cpuflags 1.34 (the issue with it not picking
it up as core2 to start with should be resolved)